Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$108.36	5.837%	$114.685	$114.69	$114.70	$114.70
Purchase #2	$91.74	9.544%	$100.4957	$100.50	$100.50	$100.50
Purchase #3	$105.61	11.857%	$118.1322	$118.13	$118.15	$118.10
Purchase #4	$19.36	6.717%	$20.6604	$20.66	$20.65	$20.70
Purchase #5	$171.58	5.211%	$180.521	$180.52	$180.50	$180.50
Purchase #6	$194.39	3.365%	$200.9312	$200.93	$200.95	$200.90
Purchase #7	$97.32	12.567%	$109.5502	$109.55	$109.55	$109.60
7 purchase totals =	$788.36		$844.9757	$844.98	$845.00	$845.00